Manufacture of cellulose



2,792,313 Ice Patented May 14, 1957 MANUFACTURE OF CELLULOSE Frank Roland Charles and Morris Wayman, Hawltesburg,

Ontario, Canada, assignors to Canadian International Paper Company, Montreal, Canada, a corporation of Quebec No Drawing. Original application April 8, 1950, Serial No. 154,896, now Patent No. 2,775,528, dated Decemher 25, 1956. Divided and this application September 27, 1956, Serial No. 616,903

6 Claims. (Cl. 106-164) lose, wood is debarked and chipped, and the wood is treated at elevated temperatures and pressures with solutions of chemicals. Such chemicals are either bisulphites, usually of calcium, magnesium or ammonium and containing an excess of free S02 in solution, or are alkaline solutions of sodium hydroxide, sodium sulphide, sodium carbonate, or mixtures of these. At the conclusion of this treatment the softened chips are disintegrated into wood pulp. Such wood pulp contains small but significant proportions of lignin, tannins and other coloring matter, and organic solvent-extractable materials such as fats, fatty acids, resmous acids, sterols and hydrocarbons. The organic solvent-extractable materials are collectively termed resin. The wood pulp produced as described above, which is mainly cellulose, is purified and bleached, and a number of processes have been described for reaching commercially acceptable levels of purity of the cellulose. As the art of purifying cellulose has improved, resulting in nearly pure cellulose with a very small content of non-cellulosic constituents, many advantages have accrued, particularly in the properties of the rayon or other derivatives manufactured from such purified cellulose. Examples of such properties are color and strength. At the same time certain difliculties have arisen in the processing of such cellulose. For example, the lowering of the resin content of rayon-grade cellulose has given rise to difficult filtration of the viscose made from it.

Simultaneously, conditions in the rayon-making industry have changed, particularly in the direction of higher speeds in various processing steps, requiring cellulose which will process more rapidly.

We have discovered that these difficulties can be overcome and a superior pulp for processing can be made by adding to the cellulose at a late stage in its manufacture one or more of the group of polyoxyethylene esters of abietic acid and hydroabietic acids. A group of compounds which we have found useful, and particularly important where yarn color is especially concerned, is the group of polyoxyethylene esters of the commercially available mixture of diand tetra-hydroabietic acids. As far as we are aware the manufacture of this last-named group of compounds for the present purpose has been cffected for the first time. These esters display remarkable stability in the viscose process, being stable under both the alkaline conditions of viscose preparation and the acid conditions of the spinning bath. This is in contrast to the behavior of fatty acid polyoxyethylene esters, which are readily attacked by alkali. The number of ethylene oxide units in the polyoxyethylene portion of these molecules can be small, merely enough to make the rosin or the mixture of diand tetrahydroabietic acid esters soluble in water, but good results are obtained with up to 100 ethylene oxide units, and best results are ob tained with 12 to 30 ethylene oxide units.

We have found that small quantities of these compounds added to the cellulose confer very marked benefits. Among advantages found in the manufacture of viscose rayon are improved steeping, less power required for shredding the alkali cellulose, more uniform adsorption of CS2 in xanthation resulting in economy of CS2, substantial reduction in unreacted fibre content of the viscose and therefore very much improved filtration of the viscose, considerable decrease in the amount of the spinneret incrustation, and improved rayon strength. Cellulose manufactured according to this invention also has special advantages in the manufacture of dull yarn made with suspensions of pigments and oils in the viscose since the suspensions are much more fine-grained and stable and the spinning proceeds with many fewer interruptions due to plugging or constriction of spinneret holes.

These esters can be added easily to the cellulose. It is simplest to apply them in a dilute aqueous solution to the cellulose at some stage in the drying of the cellulose sheet, preferably at a stage where the water accompanying the chemicals will be evaporated at a later stage in the drying. An aqueous solution of one of the esters, or of a mixture, may be sprayed on the cellulose sheet, or it may be applied by means of rolls. For accomplishing the objects of this invention it is not necessary to use more than 0.2% of ester on the weight of the cellulose, and usually 0.01% to 0.1% is sufficient.

The following two examples will illustrate preferred embodiments of this invention, but the invention must not be construed as limited to these examples.

Example 1.-A 10% aqueous solution of a polyoxyethylene ester of rosin containing 16 moles of ethylene oxide per mole of rosin was sprayed continuously all across a sheet of cellulose which was passing through a pulp-drying machine at a point where the sheet contained 50% cellulose and 50% water, at such a rate that 2 pounds of ester were sprayed on per ton of air-dry cellulose. At this rate of application all the solution was absorbed by the sheet. The sheet issuing from the drier had its normal moisture content (about 7%) and contained 0.1% ester on bone-dry cellulose. The cellulose treated in this fashion exhibited the improvements mentioned above.

Example II.A 2.85% aqueous solution of mixed polyoxyethylene esters of a commercially available mixture of diand tetrahydroabietic acids, containing an average ethylene oxide content of approximately 16.5 moles per mole of hydroabietic acid was added by means of a rotating roll to a sheet of cellulose which was passing through a pulp-drying machine. The concentration of the solution had been so adjusted that 1.4 pounds of ester per ton of bone-dry cellulose was taken up by the sheet. The point of addition in this case was where the sheet contained cellulose and 40% Water. The sheet issuing from the drier had its normal moisture content (about 7%) and contained 0.07% ester on bone-dry cellulose. The cellulose treated in this fashion exhibited the following improvements in processing into 1650 denier 720 filament high strength viscose rayon tire yarn, spinning at 100 metres per minute:

Treated Wood Untreated Pulp Wood Pulp Shredding of Alkali Cellulose: Percent Retained on mesh 2% 4%. screen after 1% hours shredding. Nature of alkali cellulose crumb Soft, fluffyv and Rather hard reactive." in feel.- Viscose Filtration:

Weight in grams filtered through 154 124. 54" diameter disc of Canton Flannel beIore filter plugged. Spinning Behavior: 7 Number of breaks per spindlc'm 3 6. 48 hours. Number of splnnerettes changed 2. s in 48 hours. Spinneret behavior All holes still A'i'cw slow clean after24 oles per hours'spin 'splnneret 11l1ig.. after- 24 hours spinning. Rayon Strength:

Grams per denier, bone-dry Percent Elongation, bone-'dry Grams per denier, conditioned. Percent Elongation, conditioned Grams per denier, wet Percent Elongation, wet

Many variations on this process will suggest themselves to those skilled in the art, but such variations are con-- sidered as falling within the scope of the invention, provided the compounds employed are within the class= However, addition even to the viscose itself We claim:

1. In the manufacture of regenerated celluloseproducts by the viscose process, the step of incorporating into viscose polyoxyethylene esters derived from the group consisting of abietic and hydroabietic acids wherein the number of ethylene oxide units in the polyoxyethylene portions of the molecules of said esters are from 12 to 100, said esters being added in an amount from 0.01% to 0.2% based on the weight of the cellulose content of the viscose.

2. In the manufacture of regenerated cellulose products by the viscose process, the step of incorporating into viscose polyoxyethylene esters of a mixtureuof diand tetra-hydroabietic acids, wherein the number of ethylene oxide units in the polyoxyethylene portions of the molecules of said esters are from 12 to 100, said esters being added in an amount from 0.01% to 0.2% based on the weight of the cellulose content of .theviscosc.

3. Viscose having incorporated therein a polyoxyethylene ester derived from the group consisting of abietic and hydroabietic acids.

4. Viscose having incorporated therein from 0.01% to'0.2%, based on the weight of cellulose in the viscose, of a polyoxyethylene ester derived from the group consisting ofabietic and hydroabietic acids and wherein the number of ethylene oxide units in the polyoxyethylene portions of the molecules is from 12 to 100.

5. In the manufacture of regenerated cellulose products by the viscose process, the step of spinning viscose in the presence ofa polyoxyethylene ester derived from the group consisting of abietic and hydroabietic acids.

6. In the manufacture of regenerated cellulose products by the viscose process, the step of spinning viscose in the presence of from 0.01% to 0.2%, based on the weight of cellulose in the viscose, of a polyoxyethylene ester derived.

No references cited. 

1. IN THE MANUFACTURE OF REGENERATED CELLULOSE PRODUCTS BY THE VISCOSE PROCESS, THE STEP OF INCORPORATING INTO VISCOSE POLYOXYETHYLENE ESTERS DERIVED FROM THE GROUP CONSISTING OF ABIETIC AND HYDROABIETIC ACIDS WHEREIN THE NUMBER OF ETHYLENE OXIDE UNITS IN THE POLYOXYETHYLENE PORTIONS OF THE MOLEUCLES OF SAID ESTERS ARE FROM 12 TO 100, SAID ESTERS BEING ADDED IN AN AMOUNT FROM 0.01% TO 0.2% BASED ON THE WEIGHT OF THE CELLULOSE CONTENT OF THE VISCOSE. 